PROBLEM: Extremely premature infants, born at 28 weeks gestation or less, are at greatest risk for poor neurodevelopmental outcomes. While survival of these infants has improved in the past decade, neurodevelopmental outcomes have not. Because early life experiences affect brain structure and function, the quality of these early life experiences is one of the most important factors affecting optimal infant development. Reliable markers of neurobiological processes underlying development are necessary so that research can accurately monitor mediators of neurodevelopmental outcomes. We propose that oxytocin has the potential to be a neurobiological marker of social processes that offer neuroprotection for the infant. Oxytocin acts as a buffer for the stress response system and provides protection to the brain during inflammation, ischemia, or injury. Oxytocin has been strongly linked to neurodevelopmental outcomes in animal models, particularly those outcomes related to social cognition and emotion regulation. No studies measuring oxytocin have been conducted in premature infants, nor has the association of oxytocin levels and neurodevelopment for these infants been investigated. The purpose of this study is to: 1) Describe the developmental trajectory of plasma oxytocin levels in premature infants through 34 weeks corrected gestational age (CGA) 2) Determine if plasma oxytocin levels vary with maternal-infant interaction and neurobehavioral organization 3) Compare oxytocin levels in plasma, urine, and saliva. METHOD: Fifty premature infants, born gestational ages 25-28 6/7 weeks, will be longitudinally followed until 36 weeks CGA. Plasma, urine, and saliva will be collected at 14 days of life, then weekly until 34 weeks CGA. Data on infant and environmental variables will be abstracted from the electronic medical record. Maternal-infant interaction will b measured by the Parent-Child Early Relational Assessment, during a videotaped feeding when the infant is at one-quarter full oral feeds. Neurobehavioral organization will be measured by the NICU Network Neurobehavioral Scale at 36 weeks CGA. SIGNIFICANCE: The findings from this study will provide information regarding 1) environmental factors that affect oxytocin levels in premature infants; and 2) the association of oxytocin levels with early indicators of neurodevelopmental outcomes. The long-term goal of this program of research is to develop and test interventions that increase oxytocin levels in extremely premature infants and, thus, improve neurodevelopmental outcomes. TRAINING PLAN: The applicant will engage in a variety of professional and educational activities at The Ohio State University and Nationwide Children's Hospital, including clinical research seminars, neonatology rounds, residencies on biological laboratory methods, coursework in circadian rhythms and stress physiology, and research meetings with affiliated Centers focused on neonatal outcomes. The breadth of the training plan supports the applicant's career goal of becoming an independent researcher.